Intravenous cannula

Abstract: A medical device, an IV cannula, has a hollow needle (4)with a sharp distal end (6) for piercing the skin of a patient includes means for protecting the sharp end (6) of the needle (4) after use to minimise the possibility of accidental needle stick. The means includes a rod (12) mounted for movement through the needle (4) between a needle end protection position and a retracted position within the hollow needle (4)*; and means for maintaining the rod towards the needle end protection position.

Description: The present invention relates to medical devices and in particular to medical devices such as intravenous cannulas which include a hollow needle having a sharp distal end for piercing the skin of a patient. The existence of infectious diseases such as AIDS and hepatitis has highlighted the danger to which medical personnel may be exposed when treating patients by means of catheter devices and syringes where a sharp needle point is used to pierce the skin of the patient. Medical personnel have been infected by physical contact with or an accidental prick by an infected needle (needle stick). In order to protect medical personnel against inadvertent needle stick a number of solutions have been developed whereby protective means incorporated within a catheter or syringe prevents physical contact with the needle after use and hence against inadvertent needle stick. Many of the developments are complicated and involve the retraction of the needle within a housing once the needle has been used. These complications add to the expense as well as the manufacturing difficulties involved in providing adequate anti-needle stick protection. It is an aim of the present invention to provide a simple but effective means for protecting the point of a needle forming part of a medical device which is an intravenous cannula in order to minimise the possibility of inadvertent needle stick. WO 89/02757 relates to a self-blunting needle assembly and device including the same. The assembly comprises a hollow needle, which may be of conventional construction having a needle mouth and a needle shank terminating in a puncture tip, has moutned within it a blunting member including an elongate probe which slidably fits within the bore of the needle shank. The probe terminates in a distal tip which is initally positioned short of the puncture tip of the needle so as not to interfere with injection of the needle either into a patient or into a connecting device. After injection, the blunting member is advanced to an extended position in which its distal tip protrudes beyond the puncture tip, thereby effectively blunting the needle. This protruding probe disables the needle from a re-use and blunts it sufficiently to rpevent or greatly reduce accidental needlestick wounds. A mechanical extension member, such as a pin or fluid flowing through the needle may be used to advance the blunting member to its extended position. According to the present invention, a medical device in the form of an intravenous cannula comprises a hollow needle having a sharpened distal end for piercing the skin of of a patient and includes means for protecting said sharpened distal end after use to minimise the possibility of inadvertent needle stick, said means comprising a rod mounted for reciprocal movement through the hollow needle between a first needle end protection position at which an end of the rod is level with or extends beyond the sharpened distal end of the needle and a second retracted position in which said end is positioned within the hollow needle and spaced from said sharpened distal end, characterised by means biasing the rod towards the first needle end protection position. Preferably, the rod is solid although it could be hollow with a blunt distal end. In one embodiment the needle extends from the distal end of a grip, the rod extending through the needle and the grip such that its proximal end extends beyond the grip, and means attached at or adjacent the proximal end of the rod is engageable by co-operating means for reciprocating the rod through said needle and grip. This means attached at or adjacent the proximal end of the rod is preferably a bobbin which is engaged by two wing members, each wing member being mounted on an individual side arm, the side arms being located one on each side of the grip, the arrangement being such that when the side arms are pressed together the wing members will cause the bobbin and hence the rod to move from the first to the second position. The maintaining means may be an elastic member extending between the side arm. An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying diagrammatic drawings in which:- Figure 1 is a perspective view of an IV cannula; Figure 2 is a plan view of the IV cannula of Figure 1; Figure 3 is a perspective view of the IV cannula of Figure 1 illustrating a cannula needle about to be inserted into the skin of a patient and including a coupling and a pair of fixation wings not illustrated in Figure 1; Figure 4 is a plan view illustrating the position of side arm of the cannula at the moment of insertion of the needle into the skin of a patient; Referring to the embodiment of the invention as illustrated in Figures 1 to 4, as shown, an IV cannula 1 includes a grip 2 from which extends a hollow needle 4 having a sharpened distal end 6. Extending through the grip 2 and the needle 4 is a solid rod 12. The rod 12 has a distal end 11 and, as shown most clearly in Figure 4, a proximal or rear end 13. Affixed at or adjacent the proximal end 13 of the rod 12 is a bobbin 16. A pair of side arms 18 is located one on each side of the grip 2 and each carries a wing member 20 engaging the bobbin 16. Connecting the rear end of the side arms 18 is an elastic member 22. As shown, the inside surface 24 of each side arm 18 bears against an enlarged flange portion 26 of the grip 2 such that without any pressure being applied to the side arms 18 said side arms 18 will naturally adopt the position illustrated in Figures 1 and 2 by virtue of the force applied by the elastic member 22 to the rear ends of the side arms 18. Before use, the cannula 1 will be as illustrated in Figures 1 and 2 with the rear ends of the side arms 18 pulled closely together and the bobbin 16 positioned flush against the rear end of the grip 2. However, when it is required that the sharpened distal end 6 of the needle 4 pierce the skin of a patient then the side arms 18 are first pressed or squeezed together as illustrated in Figure 3 against the bias of the elastic member 22. Squeezing or pressing the side arms 18 together to the position illustrated in Figure 4 will cause the wing members 20 to move the bobbin 16 and hence the rod 12 rearwardly so that the distal end 11 of the rod 12 is retracted into the hollow needle 4 and is thereby spaced from said sharpened end 6 of the needle 4. Tthis will allow the sharpened end 6 of the needle 4 to be used to pierce the skin of a patient. Once the needle 4 is removed from the body of the patient and the squeezing force removed from the side arms 18 then the elastic member 22 will apply a force to the side arms 18 bringing them back to the position shown in Figures 1 and 2. This will have the effect of the wing members 18 engaging the bobbin 16 to move the bobbin 16 and hence the rod 12 forwardly through the hollow needle 4 until the distal end 11 of the rod 12 again extends level with or beyond the sharpened distal end 6 of the needle. A particular advantage of the embodiment described above is the simplicity of the means for protecting the sharpened distal end 6 of the needle 4 which avoids the use of complicated and expensive solutions to the anti-needle stick problem.

Claims: A medical device in the form of an intravenous cannula comprising a hollow needle (4) having a sharpened distal end (6) for piercing the skin of a patient and including means for protecting said sharpened distal end (6) after use to minimise the possibility of inadvertent needle stick, said means comprising a rod (12) mounted for reciprocal movement through the hollow needle (4) between a first needle end protection position at which an end (11) of the rod (12) is level with or extends beyond the sharpened distal end (6) of the needle (4) and a second retracted position in which said end (11) is positioned within the hollow needle (4) and spaced from said sharpened distal end (6), characterised by means (18, 22) for biasing the rod (12) towards the first needle end protection position. A medical device as claimed in claim 1, in which the rod (12) is solid. A medical device as claimed in claim 1 or 2, in which the needle (4) extends from the distal end of a grip (2), the rod (12) extending through the needle (4) and the grip (2) such that its proximal end extends beyond the grip 2, and means attached at or adjacent the proximal end of the rod (12) engageable by co-operating means for reciprocating the rod (12) through said needle (4) and grip (2). A medical device as claimed in claim 3, in which the means attached at or adjacent the proximal end of the rod (12) is a bobbin (16) which is engaged by two wing members (20), each wing member (20) being mounted on an individual side arm (18), located one on each side of the grip (2), the arrangment being such that when the side arms (18) are pressed together the wing members (20) will cause the bobbin (16) and hence the rod (12) to move from the first to the second position. A medical device as claimed in claim 4, in which the maintaining means is an elastic member (22) extending between the side arms (18).

Inventors: NICHOLSON PETER JAMES, NICHOLSON, PETER JAMES
Applicants: BOC GROUP PLC, THE BOC GROUP PLC
Application year: 1994
Main classification: A61M25
IPC codes: A61M5, A61M25